This invention relates generally to a power-driven hand tool and more particularly to a hammer drill.
Hammer drills are well known in the art by this time. Generally speaking, they have a component that can be coupled with a tool, such as a drill bit, a chisel bit, or the like, and which component can be rotated, have axial blows or impacts exerted upon it so that the bit acts as a hammer, or the tool functions can be superimposed upon one another. Usually, an impactor is provided which is freely reciprocable in a tube and, when moving forwardly, impacts the rear end of the tool chuck or of a component associated therewith. Also provided is a power-driven piston which reciprocates in the same guide tube but is somewhat spaced from the impact member or angle so that a cushion of compressed air can develop between the two which transmits the kinetic energy to the angle from the piston. The prior-art constructions use an electric motor which drives a crank drive from which in turn the reciprocatory motion of the piston is derived.
This type of hammer drill is generally quite satisfactory. However, there are further improvements which it is desirable to make. In particular, the conversion of the rotary movement of the output shaft of the electric motor into a translatory motion, i.e., the reciprocation of the piston requires a rather complicated construction when it is accomplished by means of the aforementioned crank drive. At least four shafts are required, some of which have their axes inclined relative to one another, usually at right angles, and this requires the use of bevel gears, i.e. of angle drive, which is relatively complicated. Also, the use of a crank drive necessitates relatively large dimensions for the tool because of the space that is required.